This invention relates to making connections between integrated circuit array packages (IC) and circuit boards.
Ball grid array (BGA) and land grid array (LGA) packages are becoming increasingly popular because of their low profiles and high densities. With a BGA package, for example, the rounded solder balls of the BGA are generally soldered directly to corresponding surface mount pads of a printed circuit board rather than to plated thru-holes which receive pins from, for example, a pin grid array IC package.
Sockets are used to allow particular IC packages to be interchanged without permanent connection to a circuit board. More recently, sockets for use with BGA and LGA packages have been developed to allow these packages to be non-permanently connected (e.g., for testing) to a circuit board. Problems associated with attaching a BGA package to conventional sockets are discussed in U.S. Pat. No. 5,877,554, which is incorporated herein by reference. However, some of the same problems exist in attaching the socket to the circuit board. These problems occur because a BGA package presents a non-traditional mating condition. The rounded solder balls of the BGA are relatively poor points of contact for temporary connection to the circuit board and are suited oily for their intended purpose of being reflowed. Further, individual points of contact for each rounded solder ball may lack co-planarity on account of ball irregularities and warping of the circuit board.